Nonmagnetic iron-nickel-copper alloy



20 by the appended claims.

' Patented Apr. 12, 1932 loin-swing.

UNITED STATES,

PATENT OFFICE" NORMAN B. PILLING, or ELIZABETH, NEW mnsEm AsaIeNon 'ro zrnn INTERNATIONAL mcxnr. COMPANY, ING., A conronn'rroN on DELAWARE NONMAGNETIC IRON-NIOKE L-COPPER ALLOY This invention relates to nickel steels and more particularly to a copper-bearing nickel L; low magnetic permeability.

It is an object to provide such nonmagnetic compositions having corrosion-resisting properties which are also capable of being cast into tough, dense castings, or into sound, malleable ingots capable of being worked and adapted for a wide variety of uses.

These and other desired'objects and advantages of the invention will be described in the following specification, certain preferred combinations being given by way of illustration, but since the underlymg princifples apply to a wide range of proportions 0 iron, nickel and copper, it is not intended to be restricted to the particular ones shown, except as such restrictions are clearly imposed As is well known, iron, and iron containing as much as several percent of alloyed elements, is extremely subject to corrosion. by

atmospheric agencies,-a coating of hydrated iron oxide, commonly known as rust, form'- ing under the combined influence of moisture, oxygen andother gases usually present in the atmosphere. Such a coating of rust isloose, flaky and porous, and is not protective but may even accelerate further corrosion by its screening action, setting up the wellknown electrolytic oxygen concentration cells. The addition of large amounts of nickel toiron lessens the rate of such corrosion but does not change in any substantial way the nature of the rust coating-formed. Even iron-nickel alloys containing 80% of nickel will rust on exposure to moist air containing traces of sulphurous gases. The rust coating thus formed is thin but flaky, readily splitting oil from the surface, or spalling and corrosion proceeds at'a slow rate but unchecked. With intermediate c'on tents of'nickel, as 30% or 50%, the flaky, nonprotective type of rust coating. forms, with corrosion rates about proportional to the iron content. I have found that the addition of copper to iron-nickel alloys has amarked efiect on "Application filed November 16, 1928.. Serial No. 319,999.

the physical structure of the corrosion product formed on atmospheric exposure, whereby the pronounced flaking. properties and porosity are eliminated and a tight, dense, iighly adherent coating results, such that further corrosion is greatly retarded or practically stopped. The result of this is I that articles made from alloys lying within the range of compositions described below show an excellent durability when continuously exposed to-corrosion innatural atmospheres, even those contaminated by smoke or other industrial gases. The presence of copper, with its attendant change in. adherence'of the natural corrosion product, is to be considered not merely a permissible replacement of an equal amount of nickel, but as allowing a very substantial reduction in the total non-ferrous content to'obtain an equivalent degree of atmospheric corrosion resist-- ance. As concrete examples, an exposure test conducted in the open air for a period of several years showed that an iron-nickelcopper alloy containing 25% nickel, 5% copper, was equal in durability'to an iron-nickel.

alloy containing 50% nickel; again, anironnickel-copper alloy containing 50% nickel,

9% copper, was the equivalent of an ironnickel alloy containing nickel. These examples show the economy which the addition of copper to iron-nickel alloys permits.

The alloys of the present invention com prise compositions containing the following elements in substantially the proportions enumerated, viz: nickel, 12-30%, copper, 120%, carbon, .O1-2%, the balance substantially iron. The nickel should be equal to or greater than 1.5 times the copper content. Carbon, in the case of compositions in which the ratio of the nickel content to the nickel plus'iron contents is less than .27 is defined as follows N 5(- JV-T-T') in which C is the minimum percentage of carbon desired, N the percentage of nickel, and F the percentage of iron. ilicon, manganese, and other elements commonly used to aid in securing sound, malleable ingots may be present. It will be observed, of 2%, depending upon the use which the course, that the ratiov of alleyhis to be put.

. v N ile excellent malleable alloys have been m produced containing .03% carbon, a consldv erably higher content may be tolerated 1n the must not be-greater'than .270 otherwise the malleable grades. In generaLincreasin the above equation will give a negative value. carbon content increases the hardness o? the :Alloys lymg'within this range of composialloy and also diminishes somewhat its cold 'tions having aratio of nickel to nickel plus workability; It is usually preferable to limit iron contents less than .30 are substantially the carbon content to 30%; at .50%, the pro-" non-magnetic, respond very feebly if at 'all' clpitation of graphite begins, which tends to t a magnet and are adaptedto many usesdlmmish ductility; alloys intended to be,

in the electrical industry which the more exm l ble Should contain le s than 1%, but

' pensive copper. alloys nowfill. It is necesing may n in p to carbon;

sary to provide carbon exceeding the limit A-hlgh carbon content does not materially 1 7 *specified inthe preceding paragraph in order H affect the corrosion resistance. While high to retain the alloys in the non-magnetic con carbon alloys are lestllcted' g 1t dition. With insufficient carbon they become po with P y precautions to "strongly magnetic. tam castings with as little as .1% carbon.

The alloys comprised within the above It is'apparent from-this that the higher ranges are sort, that is, have a Brinell hardca content a l ys hav a wi r rang f ness number not greater than 175 and all m hehcopper contents which are non-mag-. have the common property of resistance to netlc h the lower carbon q nt y corrosion. Their resistance to atmospheric and'whllcon the o her h n mcreasmg the corrosion has been described above. To other on contentincreases the hardness, an -forms of corrosion, I have found the addithat Whlle a g pp content glves tion of copper to iron-nickel alloys to be an. greater corrosive resistahe, i lessens the I advantage, owing to the lowered solution p workability. For 'a'. particular application tential re ulting. Thi i p t h thebest compositlon therefore depends upon been noted in many dilute nonoxidizing acids the eXteIit o which these opposing ten e 'i and in various salt solutions. must be b a In general, the. hardness and strength AS a particular ex ple the alloy con properties do not vary to any substantial g- 5 0 pp -h% amount in going from one extreme of com- 11.959 carbon m y be clted; T 85 position to another, but the corrosion resisthas a r io of mckel nickel plus 1ron oi ance does alloys the -2 7 from the 0f ranges of iron contents will have is-much Should benoh'maghetlc Y h lower resistance to corrosion'than those lying aid of m qar It was 111 h within the low iron ranges; there is no sudwholly non'magnetlc'fiven after p q den change in order of magnitude',.but a It had fl tmg P p v gradual, continuous, increasin d f made 'I'rom 1t forged perfectlyto slabs whlch corrosion resistance as theniekel mt m; 'c0ld-1 1 leadll t0 h p, non-magnetlc the copper content is increased. On the other P The P h h hflrdhess of hand, certain properties do change greatly Q 9 he mach1ned w h (hihculty y no within these limits, requiring. a restriction of dnlhhgs i g 3 hg l h 1t composition to gain certain ends. The hot responded m x weldmg W elthel the malleability i l l a tt f copper oxyacetylene flame or electric-arc, as well c t t, d alloys containing m' to resistance or, spot weldmg; t accepted sol- 5 12% of copper are forgeable and otherwise, dam and braze-s 1 7 an 18 m fact muted workable onl with much difiiculty. Alfor use as an.engmeermg-anoy-' Expmd to though showing a high degree of resistance g 5 K smoky thm sh to corrosion, they are of value chiefiyin the. i fi p h 33 mg u form of castings. When articles shapedbylf m goo P yslca 9 1on1 I These alloys have a hlgh electrical reslstlvworking are required, it is preferable and are Suitable for use in deemed have the'copper content less than 12% -an'd= ure y when the highest degree of malleability ma g j f ggg ggfi gf ductility is'required, I limit the copper con' 3 It ill n b en that'ther'ehas'beei tent to 6%. The processfor improving the id d a grou f ll y om 'tionsconi 60 malleability of nickel alloys disclosed in my ing iron, nic e1, copper an carbo'n'whic are m co-pending application, Serial Number 223,- characterized by the pro ertiesof low 233, 13 of material service.- for corrosion, particulariy an atmospheric The effect of variations in nickel, copper exposure, and ready workabili (1n and iron content have already been discussed. lower ranges of copper content) w 'ch are at 1 The carbon content may range from' .01% to thejsame time substantially It will be observed that the present invention provides an alloy comprising copper about 1% to about 20%, nickel not exceeding about 22% and extending to about 12%, carbon exceeding about 0.4% and being under 2.0%, and the remainder consisting principally of iron which is not only non-ma etic but which is also of substantially uniform softness. g 5 What I claim is: v

1. A nonmagnetic alloy comprising copper about 1% to about 20%, nickel not exceeding about 22% and extending to about 12%, carbon exceeding about 0.4% and bein un- 15 der about 2.0%, and the remainder consisting principally of iron whereby an alloy is produced which is nonmagnetic and which is of substantially uniform softness. 2. A nonmagnetic alloy comprising copper 0 about 1% to about nickel not exceedmg about 22% and extending to about 12%; carbon about 0.5%, and the remainder consisting principally of iron whereby an alloy is produced which is nonmagnetic and which is 25 of substantially uniform softness.

In testimony whereof I have hereunto set my hand.

, NORMAN B. PILLIN G. 

